<div id="app">
<template v-if="loginType">
  <label>Username</label>
  <input placeholder="Enter your username" key="username-input">
</template>
<template v-else>
  <label>Email</label>
  <input placeholder="Enter your email address" key="email-input">
</template>
  <div>
    <button v-on:click="changeType">toggle login type</button>
  </div>
</div>
var vm = new Vue({
  el: '#app',
  data: {
    loginType: true
  },
  methods:{
    changeType: function(){
      this.loginType=!this.loginType;
    }
  }
})

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.min.js